1. Field of the Invention
This invention is related to providing high availability for an application.
2. Description of the Related Art
Certain applications are often required to be available virtually uninterrupted, either 24 hours a day or at least during working hours. Various efforts have been undertaken to provide high availability services to support the high availability of such applications. Such highly-available applications may include email servers, web servers, databases, etc.
Typically, efforts to provide high availability for a given application have focused on detecting that the application has failed on a system, and getting the application re-started on the same system or a different system. Clustering solutions have been attempted in which a group of computer systems are clustered using specialized software (referred to as a cluster server) to control the group of computer systems. A given application executes on a first computer system of the cluster, and the cluster server monitors the operation of the application. If the cluster server detects that the application has failed, the cluster server may close the application on the first computer system and restart the application on another computer system in the cluster. While clustering solutions have had success in providing high availability, these solutions may result in low utilization of the computer systems in the cluster that are not actively executing the application. Generally, each of the computer systems in the cluster may have the resources required to execute the application (e.g. proper operating system, drivers, etc. including having the proper versions of the various software). Thus, applications requiring differing resources may not typically execute on the same cluster. For example, the resources for different applications may conflict (e.g. different operating systems, different drivers, or different versions of the foregoing). In some cases, applications requiring similar resources may execute on the same cluster, but in many cases the utilization may be low.